1. Field of the Invention
The subject invention relates to a needle guard for enclosing and protecting a needle cannula to avoid accidental sticks and to prevent contamination of the needle cannula prior to use.
2. Description of the Prior Art
A prior art needle cannula is a long narrow metal tube having opposed proximal and distal ends and having a lumen extending between the ends. The distal end of the prior art needle cannula typically is beveled to define a pointed cutting edge that is sufficiently sharp to pierce the skin of a patient or to penetrate a piercable membrane that seals a container of medicine. The proximal end of the needle cannula typically is secured to a structure that will enable fluid communication through the lumen. For example, some prior art needle cannulas are rigidly and permanently connected to the distal end of a hypodermic syringe barrel. Other prior art needle cannulas are securely mounted to a hubs which in turn can be threadedly engaged with the distal end of a prior art syringe barrels.
It is well known that needle cannulas are capable of transmitting disease or infection. For example, an accidental stick with a used needle cannula can transmit disease from the patient on whom the needle cannula had been used. An accidental stick with an unused needle cannula can leave an open wound that is subject to infection if not treated properly. Infection or disease also can be transmitted by means other than an accidental stick. For example contact with an intermediate portion of a needle cannula prior to use can impart contaminants to the outer surface of the needle cannula. These contaminants may be transferred to the patient when the needle cannula is used. Similarly, contact with a side wall region of a used needle cannula can possibly result in a transfer of infectious bodily fluids.
Most needle cannulas are provided with guards or shields that are intended to prevent accidental needle contact. Some needle shields include an elongate rigid shield having an open proximal end and a closed distal end. The shield is mounted over the needle cannula in a distal-to-proximal direction and is frictionally retained on the needle hub or on distal regions of a syringe barrel. The shield can be removed immediately prior to use by exerting a distally directed force on the shield relative to the needle cannula. Shields of this type are very effective and are commonly used for avoiding needle sticks prior to the initial use of a needle cannula. However, it is generally recommended not to use this type of shield after injection because of the possibility of needle sticks during the reshielding process.
Some prior art needle cannulas are provided with a hinged guard. The prior art hinged needle guard may define a generally U-shaped channel having a proximal end that is hingedly articulated to or near the needle hub. The needle guard may be rotated from a first position where the needle cannula is exposed for use to a second position where the needle cannula is partly surrounded by the needle guard. Prior art hinged needle guards are effective for preventing accidental needle sticks. Additionally, prior art needle guards substantially reduce the possibility of inadvertent contact with side wall regions of the needle cannula. However, one longitudinal side of the needle cannula is left exposed by the prior art hinged needle guard. Thus, environmental materials may be able to contact this needle cannula before the initial use.
The prior art hinged needle guard typically will prevent inadvertent contact with any portion of the needle cannula after use. However, the long thin needle cannulas can be bent during use or by inadvertent contact with a hard surface immediately after use. In these situations, the portions of the bent needle cannula may project from the open side of the prior art hinged needle guards. The greatest deviation from a perfect axial alignment is likely to be at the distal tip of the bent needle cannula. Thus, the pointed distal tip could be exposed from the prior art hinged needle guard and could accidentally stick a health care worker who reasonably assumed that the needle was safely enclosed within the prior art hinged guard.